Corrosion inhibiting compositions and coatings including the same

ABSTRACT

A corrosion inhibiting composition includes a first plurality of carriers and a second plurality of carriers. The first plurality of carriers has a first carrier body which encapsulates a film-forming compound. The second plurality of carriers has a second carrier body encapsulates a corrosion inhibitor. Each of the first and second carrier bodies is formed of a degradable material. Coatings and methods for inhibiting corrosion on a metal substrate are also described herein.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and is a divisional of U.S. patent application Ser. No. 13/841,393 filed Mar. 15, 2013. The disclosure of the prior application is hereby incorporated in its entirety by reference herein.

TECHNICAL FIELD

The present disclosure generally relates to corrosion inhibiting compositions and methods of making and using such compositions, in particular compositions including film-forming compounds and corrosion inhibitors.

BACKGROUND

Many metals and metal alloys are subject to corrosion that causes these metals and metal alloys to lose their structural integrity. As such, methods have been developed to detect the presence of corrosion and to attempt to prevent or inhibit it.

SUMMARY

In one embodiment, a corrosion inhibiting composition includes a first plurality of carriers and a second plurality of carriers. Each of the first plurality of carriers includes a first carrier body and a film-forming compound. The first carrier body encapsulates the film-forming compound. The first carrier body is formed of a first degradable material. Each of the second plurality of carriers includes a second carrier body and first corrosion inhibitor. The second carrier body encapsulates the first corrosion inhibitor. The first corrosion inhibitor comprises an organic compound including a ring structure. The second carrier body is formed of a second degradable material.

In another embodiment, a corrosion inhibiting composition includes a first plurality of carriers and a second plurality of carriers. Each of the first plurality of carriers includes a first carrier body and a film-forming compound. The first carrier body encapsulates the film-forming compound. The first carrier body is formed of a first degradable material. Each of the second plurality of carriers includes a second carrier body and first corrosion inhibitor. The second carrier body encapsulates the first corrosion inhibitor. The second carrier body is formed of a second degradable material. The first plurality of carriers and the second plurality of carriers have different average outer diameters.

In still another embodiment, a corrosion inhibiting composition includes a first plurality of carriers, a second plurality of carriers, and third plurality of carriers. Each of the first plurality of carriers includes a first carrier body and a film-forming compound. The first carrier body encapsulates the film-forming compound. The first carrier body is formed of a first degradable material. Each of the second plurality of carriers includes a second carrier body and first corrosion inhibitor. The second carrier body encapsulates the first corrosion inhibitor. The first corrosion inhibitor comprises a first organic compound including a ring structure. The second carrier body is formed of a second degradable material. Each of the third plurality of carriers includes a third carrier body and a second corrosion inhibitor. The third carrier body encapsulates the second corrosion inhibitor. The second corrosion inhibitor comprises a second organic compound including a ring structure. The second corrosion inhibitor is different from the first corrosion inhibitor. The third carrier body is formed of a third degradable material

In yet another embodiment, a coating for inhibiting corrosion on a metal surface includes a coating base and a corrosion inhibiting composition. The coating base includes an organic layer. The corrosion inhibiting composition is dispersed in the coating base. The corrosion inhibiting composition includes a first plurality of carriers and a second plurality of carriers. Each of the first plurality of carriers includes a first carrier body and a film-forming compound. The first carrier body encapsulates the film-forming compound. The first carrier body is formed of a first degradable material. Each of the second plurality of carriers includes a second carrier body and first corrosion inhibitor. The second carrier body encapsulates the first corrosion inhibitor. The first corrosion inhibitor comprises an organic compound including a ring structure. The second carrier body is formed of a second degradable material.

In yet still another embodiment, a method for inhibiting corrosion on a metal substrate includes applying a coating to a metal substrate. The coating includes a coating base and a corrosion inhibiting composition. The coating base includes an organic layer. The corrosion inhibiting composition is dispersed in the coating base. The corrosion inhibiting composition includes a first plurality of carriers and a second plurality of carriers. Each of the first plurality of carriers includes a first carrier body and a film-forming compound. The first carrier body encapsulates the film-forming compound. The first carrier body is formed of a first degradable material. Each of the second plurality of carriers includes a second carrier body and first corrosion inhibitor. The second carrier body encapsulates the first corrosion inhibitor. The first corrosion inhibitor comprises an organic compound including a ring structure. The second carrier body is formed of a second degradable material.

In another embodiment, a corrosion inhibiting composition a first plurality of carriers and a second plurality of carriers. Each of the first plurality of carriers includes a first carrier body and a film-forming compound. The first carrier body encapsulates the film-forming compound. The first carrier body has a first average diameter and is formed of a first degradable material. Each second plurality of carriers includes a second carrier body and a corrosion inhibitor. The second carrier body encapsulates the corrosion inhibitor. The second carrier body is formed of a second degradable material and has an average diameter that is larger than the first average diameter.

In yet another embodiment, a method for inhibiting corrosion on a metal substrate includes applying a coating to a metal substrate. The coating includes a coating base and a corrosion inhibiting composition. The coating base includes an organic matrix. The corrosion inhibiting composition is dispersed in the coating base. The corrosion inhibiting composition includes a first plurality of carriers and a second plurality of carriers. Each of the first plurality of carriers includes a first carrier body and a film-forming compound. The first carrier body encapsulates the film-forming compound. The first carrier body has a first average diameter and is formed of a first degradable material. Each second plurality of carriers includes a second carrier body and a corrosion inhibitor. The second carrier body encapsulates the corrosion inhibitor. The second carrier body is formed of a second degradable material and has an average diameter that is larger than the first average diameter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a corrosion inhibiting composition having a plurality of carriers.

FIG. 2 illustrates one embodiment of a carrier having a carrier body and a film-forming compound.

FIG. 3A illustrates one embodiment of a carrier having a carrier body and a corrosion inhibitor.

FIG. 3B illustrates another embodiment of a carrier having a carrier body and a corrosion inhibitor.

FIG. 4 illustrates one embodiment of two carriers, one having a film-forming compound and the other carrier having a corrosion inhibitor.

FIG. 5 illustrates one embodiment of a plurality of carriers, one having a film-forming compound and the other carriers having different corrosion inhibitors.

FIG. 6 illustrates an embodiment of a coating system applied to a surface of a metal body portion of a vehicle.

FIG. 7 illustrates the Adhesion Test procedure used to measure the creep value of a test piece (e.g., metal substrate).

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, logical, and chemical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims and equivalents thereof.

FIG. 1 generally illustrates a corrosion inhibiting composition 10. The corrosion inhibiting composition 10 can be applied to a metal surface (as indicated in FIG. 5), such as a vehicle body. As shown in FIG. 1, the composition 10 can include a plurality of carriers 15.

In general, each carrier 15 can be a microparticle or microcapsule that can be included in a protective coating. Such protective coating can then be applied to a metal substrate and cured thereon, so that any mechanical damage or corrosive damage to the resultant coating can cause the carrier to rupture or otherwise fail so that a repair or protective substance is released and deployed into or onto the damaged area of the coating, for example, to the exposed surface of a metal substrate. In a non-limiting example, the carrier 15 can have a substantially spherical configuration. It will be appreciated that such carriers 15 can form spherical particles, including but not limited to, microspheres, microcapsules, microparticles, nanospheres, nanocapsules and nanoparticles. However, the carrier is not limited to spherical particles, as one of ordinary skill in the art will appreciate that a variety of different shapes may be used for the carrier. Illustrative examples include, rods, fibers, tubes or elongated capsules.

FIGS. 2, 3A and 3B are enlarged, non-limiting, views of carrier 15. As shown in FIG. 2, carrier 15 can include a carrier body 17 and at least one film-forming compound 21. As shown in FIGS. 3A and 3B, carrier 15 can include a carrier body 17 and at least one organic corrosion inhibitor 20. As shown in FIG. 2, the carrier 15 is in the form of a microcapsule such that the carrier body 17 encircles and encapsulates the least one film-forming compound 21 therein. The film-forming compound 21 can be a liquid, solid, or a gas entrapped in aerogel or various combinations thereof. For certain embodiments, a film-forming compound is dissolved or dispersed in a hydrophobic substance, such as oil, or a hydrophilic substance, such as water, optionally with one or more active substances such as a corrosion inhibitor. For certain embodiments, the carrier 15 can contain only active substances such as film forming compounds 21 and organic corrosion inhibitors 20 (see FIGS. 3A and 3B).

In certain embodiments, the carrier body 17 of the carrier 15 can comprise gelatin, polyurethane, urea formaldehyde, melamine formaldehyde, melamine formaldehyde/pentaerythritol tetrakis or a suitable combination thereof. In certain embodiments, the carrier body 17 can be formed having a multi-walled shell.

Each carrier can have a substantially spherical shape with an average outer diameter up to 50 gm. In certain embodiments, each carrier has an average outer diameter ranging from about 100 nm to 15 gm. In certain embodiments, each carrier has an average outer diameter ranging from about 0.5 gm to 10 gm. In certain embodiments, each carrier has an average outer diameter of about 5 gm or less. In certain embodiments, each carrier has an average outer diameter ranging from about 1 gm to 2 gm. The average outer diameter of each carrier can be measured using a variety of suitable techniques, including for example, optical microscopy and laser diffraction.

For carriers encapsulating a film-forming compound, such carriers can have an average diameter larger than the average diameter of a carrier encapsulating a corrosion inhibitor. In certain embodiments, a carrier comprising a film-forming compound can have an average diameter from about 3 microns to about 15 microns; in certain embodiments from about 5 microns to about 10 microns; and in certain embodiments from about 6 microns to about 8 microns. In certain embodiments, a carrier comprising a corrosion inhibitor can have an average diameter up to about 5 microns; in certain embodiments up to about 3 microns; and in certain embodiments from about 0.5 micron to about 2 microns.

Each carrier 15 can having a carrier body 17 formed from a degradable material. For example, the mechanical integrity of the carrier body 17 can break down, disintegrate or otherwise deteriorate in the presence of a base (or an alkaline), e.g., having a pH of about 8 or above, such that the carrier body 17 is breached and the film-forming compound 21 is released from the carrier 15. In certain embodiments, the carrier body 17 can be breached due to mechanical damage to the carrier body 17 (e.g., rupture, fracture, scratching, etc.). It will be appreciated that carrier body 17 for each carrier 15 can be formed from different degradable materials. It will also be appreciated that once the carrier body 17 degrades; the film-forming compound 21 can be released to the environment adjacent to the carrier 15.

Carriers 15 having carrier bodies 17 that break down under basic, or alkaline, conditions or rupture due to mechanical damage are generally known in the art. It is the interaction of alkaline conditions with functional groups of the cross-linking agent that causes carrier body 17 to break down or disintegrate under alkaline conditions. Alternatively, the film-forming compound 21 can be released mechanically, such as by scratching or applying pressure to the carrier body 17 of the carriers 15 in the corrosion inhibiting composition 10 or to a coating to which the corrosion inhibiting composition 10 is applied.

A basic, or alkaline, condition often forms in the presence of corrosion in a metal or a metal alloy, e.g., a basic condition often forms next to corrosion-induced pits, crevices, etc. For example, when a drop of salt water is applied to steel, an anodic reaction can occur to produce a rust spot, and a cathodic reaction (the reduction reaction of the oxygen in the presence of water), can occur to produce a basic condition. Therefore, when a coating, containing the corrosion inhibiting composition 10, is applied to a metal substrate, and if corrosion occurs, carrier bodies 17 of the plurality of carriers 15 can be exposed to the basic condition (e.g., alkaline) and will break down or disintegrate under the basic condition resulting from the corrosion, thereby releasing film-forming compounds 21. Corrosion can include any chemical or electrochemical process involving the deterioration or degradation of metals, including pitting, crevice corrosion, dissimilar metal corrosion, or the like.

An acidic condition often forms in the presence of corrosion in a metal or a metal alloy, e.g., an acidic condition often forms at corrosion-induced pits, crevices, etc. For example, when a drop of salt water is applied to steel, an anodic reaction can occur to produce an acidic condition, and a cathodic reaction (the reduction reaction of the oxygen in the presence of water), can occur to produce a basic condition. Therefore, when a coating, containing the corrosion inhibiting composition 10, is applied to a metal substrate, and if corrosion occurs, carrier bodies 17 of the plurality of carriers 15 can be exposed to the acidic condition and will break down or disintegrate under the acidic condition resulting from the corrosion, thereby releasing film-forming compounds 21. Corrosion can include any chemical or electrochemical process involving the deterioration or degradation of metals, including pitting, crevice corrosion, dissimilar metal corrosion, or the like. In a non-limiting example, both a mixture of alkaline and acidic degradable polymer carriers 15 can be used. It is to be understood that the same corrosion inhibitor can be used in both types of carriers or different corrosion inhibitors can be used in an acidic degradable carrier and alkaline degradable carrier.

Microcapsules as described above can be formed using a variety of suitable methods. For example, a microcapsule can be formed by forming an oil (e.g., toluene, vegetable oil) in water emulsion. A surfactant, such as xanthan gum, Attagel 40 (available from Engelhard Corporation, Iselin, N.J., USA), Petro BAF (available from Akzo Nobel Chemicals, Inc., Chicago, Ill., USA), and/or Reax 83 (available from MeadWestvaco Corporation, Stamford, Conn., USA) can be added to the emulsion to evenly distribute the oil in the water. A pre-polymer (e.g., an amino resin pre-polymer), a cross-linking agent having one or more ester or thioester groups that are broken down under alkaline conditions, and the organic corrosion inhibitor 20 call then be added to the oil phase. A catalyst (e.g., all inorganic acid) can be added to the water phase. The oil in water emulsion can then be heated, causing a polymerization reaction to occur at the water-oil interface, thus allowing for the formation of the carrier body 17 around film-forming compound 21 to form the carrier 15.

In a non-limiting example shown in FIG. 3A, the carrier 15 can be a microparticle including the organic corrosion inhibitor 20, and optionally one or more other active ingredients. As shown in FIG. 3A, the carrier body 17 of the carrier 15 can be a solid binder that contains (e.g., encapsulates) the organic corrosion inhibitor 20. The organic corrosion inhibitor 20 can be a liquid, solid, or a gas entrapped in aerogel or various combinations thereof For certain embodiments, the organic corrosion inhibitor 20 can be dissolved or dispersed in a hydrophobic substance, such as oil, or a hydrophilic substance, such as water, and optionally one or more active substances such as corrosion indicator, inorganic corrosion inhibitor, film-forming compound, or various combinations thereof. For certain embodiments, the carrier 15 contains only active substances such as the organic corrosion inhibitor 20, and optionally corrosion indicators, film-forming compounds, or various combinations thereof.

The solid binder forming the carrier body 17 of the microparticle carrier 15 as shown in FIG. 3A, can comprise gelatin, polyurethane, urea formaldehyde, melamine formaldehyde, melamine formaldehyde/pentaerythritoltetrakis or a suitable combination thereof.

The microparticle carrier 15 shown in FIG. 3A can include a carrier body 17 comprising a solid binder formed from a degradable material. For example, the mechanical integrity of the solid binder can break down, disintegrate or otherwise deteriorate in the presence of a base (or an alkaline), e.g., having a pH of about 8 or above, such that the solid binder is breached and the organic corrosion inhibitor 20 is released from the carrier 15. In certain embodiments, a solid binder can be breached due to mechanical damage to the solid binder (e.g., rupture, fracture, scratching, etc.). It will be appreciated that the solid binder for each carrier body 17 of each carrier 15 can be formed from different degradable materials. It will also be appreciated that once a solid binder degrades the organic corrosion inhibitor 20 can be subsequently released to the environment adjacent to the carrier 15.

Microparticle type carriers 15 having carrier body 17 formed of a solid binder that breaks down under basic, or alkaline, conditions or rupture due to mechanical damage are known in the art. Such microparticles can be formed using a variety of suitable methods. A basic, or alkaline, condition often forms in the presence of corrosion in a metal or a metal alloy, e.g., a basic condition often forms next to corrosion-induced pits, crevices, etc. For example, when a drop of salt water is applied to steel, an anodic reaction can occur to produce a rust spot, and a cathodic reaction (the reduction reaction of the oxygen in the presence of water), can occur to produce a basic condition. Therefore, when a coating, including the corrosion inhibiting composition 10, is applied to a metal substrate, and if corrosion occurs, the solid binders forming the carrier bodies 17 of the microparticle carriers 15 can be exposed to the basic condition (e.g., alkaline) and will break down or disintegrate under the basic condition resulting from the corrosion, thereby releasing the organic corrosion inhibitor 20. Corrosion can include any chemical or electrochemical process involving the deterioration or degradation of metals, including pitting, crevice corrosion, dissimilar metal corrosion, or the like.

In a non-limiting example shown in FIG. 3B, the carrier 15 can be a polymer particle (e.g., a polymer microparticle and a polymer nanoparticle) including the organic corrosion inhibitor 20, and optionally one or more other active ingredients. As shown in FIG. 2C, the carrier body 17 of the carrier 15 can be at least one polymer chain that contains (e.g., encapsulates) the organic corrosion inhibitor 20. In one embodiment, the carrier body 17 can be formed of a high pH responsive polymer (HPRP). The HPRP can have a number average molecular weight of about 2,500 to about 5,000. The organic corrosion inhibitor 20 can be a liquid, solid, or a gas entrapped in aerogel or various combinations thereof For certain embodiments, the organic corrosion inhibitor 20 can be dissolved or dispersed in a hydrophobic substance, such as oil, or a hydrophilic substance, such as water, and optionally one or more active substances such as corrosion indicator, inorganic corrosion inhibitor, film-forming compound, or various combinations thereof. For certain embodiments, the carrier 15 contains only active substances such as the organic corrosion inhibitor 20, and optionally corrosion indicators, film-forming compounds, or various combinations thereof.

The polymer particle carrier 15 shown in FIG. 3B can include a carrier body 17 comprising at least one polymer chain (e.g., HPRP with carboxylic acid end groups and a hydrophilic segment) formed from a degradable material. For example, the mechanical integrity of the polymer chain(s) can break down, disintegrate or otherwise deteriorate in the presence of a base (or an alkaline), e.g., having a pH of about 8 or above, such that the solid binder is breached and the organic corrosion inhibitor 20 is released from the carrier 15. It will be appreciated that the polymer chain(s) for each carrier body 17 of each carrier 15 can be formed from different degradable materials. It will also be appreciated that once a polymer chain degrades (e.g., breaks apart) the organic corrosion inhibitor 20 can be subsequently released to the environment adjacent to the carrier 15.

Polymer particle type carriers 15 having carrier body 17 formed of a polymer chain that breaks down under basic, or alkaline, conditions or rupture due to mechanical damage are known in the art. Such polymer particles can be formed using a variety of suitable methods, including, for example, a phase inversion method. For example, the organic corrosion inhibitor 20 can be dispersed between the entangled polymer chains that form the carrier body 17. A basic, or alkaline, condition often forms in the presence of corrosion in a metal or a metal alloy, e.g., a basic condition often forms next to corrosion-induced pits, crevices, etc. For example, when a drop of salt water is applied to steel, an anodic reaction can occur to produce a rust spot, and a cathodic reaction (the reduction reaction of the oxygen in the presence of water), can occur to produce a basic condition. Therefore, when a coating, including the corrosion inhibiting composition 10, is applied to a metal substrate, and if corrosion occurs, the polymer chains forming the carrier bodies 17 of the carriers 15 can be exposed to the basic condition (e.g., alkaline) and will break down or disintegrate under the basic condition resulting from the corrosion, thereby releasing the organic corrosion inhibitor 20. Corrosion can include any chemical or electrochemical process involving the deterioration or degradation of metals, including pitting, crevice corrosion, dissimilar metal corrosion, or the like.

In certain embodiments, an organic corrosion inhibitor can comprise from about 15% to about 50%, by weight, of a carrier; in certain embodiments, from about 20% to about 40% by weight, of a carrier; and in certain embodiments from about 20% to about 35%, by weight, of a carrier.

Once the carrier body 17 of the carrier 15, including any of those illustrated in FIG. 2, 3A or 3B, has degraded, a repair substance and/or an anti-corrosion substance can be released.

Repair substances, such as film-forming compounds can fill voids in the original coating to seal and protect the damaged area. These film-forming compounds can be released from carriers (e.g., microcapsules or microparticles) once the encapsulant (e.g., carrier body) becomes damaged. Such suitable film-forming compounds can include a clear varnish (e.g., an acrylic varnish), epoxy resins, polar aprotic solvents, siloxane resins (e.g., polydimethylsiloxane), linseed oil, tung oil, silyl ester, iscocyanates, or combinations thereof other suitable film-forming compounds can include polybutenes, phenolics, phenolic varnishes, long chain polyester diluents, carrier diluents, and combinations thereof. Other suitable film-forming compounds are further described in U.S. Patent Application Publication Nos. 2006/0042504, 2008/0152815, 2012/0000810 and 2012/0052307.

Without being limited to any particular theory, an organic corrosion inhibitor can use one or more mechanisms to provide the requisite corrosion protection, including for example, absorption and adsorption. Organic corrosion inhibitors can include, but are not limited to, organo phosphonates (including, but not limited to phenyl phosphonic acid), amine compounds (including, but not limited to triethanolamine and dodecylamine), imadazole compounds (including, but not limited to benzoimidazole, and 2-phenilimidazoline), oxazole compounds, indazole compounds, triazole compounds (including, but not limited to benzotriazole), pyrazole compounds (including, but not limited to 3-Methyl-5-pyrazolone), thiazole compounds (including, but not limited to 2-Mercaptobenzothiazole), quinoline and quinolone compounds (including, but not limited to 8-Hydroxyquinoline, and 8-Hydroxyquinaldine), their derivatives, and combinations thereof. Certain corrosion inhibitors are also described in U.S. patent application Ser. No. 13/839,895, filed Mar. 15, 2013, which is hereby incorporated herein by reference in its entirety.

In certain embodiments, as illustrated in FIG. 4, a corrosion inhibiting composition can include a first carrier 15 a and a second carrier 15 b. The first carrier 15 a can include a first carrier body 17 a and a film-forming compound 21. The first carrier 15 a can be formed from a microcapsule. The second carrier 15 b can include a second carrier body 17 a and a corrosion inhibitor 20 b. The second carrier 15 b can be formed from a microparticle.

In certain embodiments, a corrosion inhibiting composition can include a plurality of carriers, each having a carrier body and a corrosion inhibitor encapsulated by the carrier body. The corrosion inhibitor can include an organic compound including a ring structure. The carrier body can be formed of a degradable material. In a non-limiting example, the corrosion inhibitor can be a chelating agent or capable of acting as a chelating agent. For example, the corrosion inhibitor may have a plurality of donor atoms. In a non-limiting example, the corrosion inhibitor can include an organic compound such as a heterocyclic compound with an endocyclic donor atom and an exocyclic donor atom. For example, the corrosion inhibitor may include a heterocyclic compound with an exocyclic donor atom directly bonded to the heterocyclic compound (e.g., 2-Mercaptobenzothiazole and 3-Methyl-5-pyrazolone), or an exocyclic donor atom that is not directly bonded to the heterocyclic ring (e.g., 8-Hydroxyquinoline and 8-Hydroxyquinaldine). In a non-limiting example, the carrier body can comprise gelatin, polyurethane, urea formaldehyde, melamine formaldehyde/pentaerythritol tetrakis or a suitable combination thereof. In certain embodiments, the plurality of carriers can form microparticles.

In an embodiment shown in FIG. 4, the corrosion inhibiting composition 10 can include a first carrier 15 a having a film-forming compound 21, a second carrier 15 b including a first corrosion inhibitor 20 b, and a third carrier 15 c including a second corrosion inhibitor 20 c that is different from the first corrosion inhibitor 20 b. In certain embodiments, the corrosion inhibiting composition 10 will comprise a first plurality of carriers 15 a and a second plurality of carriers 15 b, and optionally a third plurality of carriers 15 c.

As generally represented by FIG. 4, the second carrier 15 b can include the first corrosion inhibitor 20 b that is an organo phosphonate, and the third carrier 15 b can include the second corrosion inhibitor 20 c that is an organic compound including a ring structure. In a non-limiting example, the organo phosphonate can be a phosphonic acid derivative (e.g., phenyl phosphonic acid). In a non-limiting example, the second corrosion inhibitor can be a chelating agent or be capable of acting as a chelating agent. For example, the second corrosion inhibitor may have a plurality of donor atoms. In a non-limiting example, the second corrosion inhibitor 20 c can include a heterocyclic compound with an endocyclic donor atom and an exocyclic donor atom. For example, the second corrosion inhibitor 20 c may include a heterocyclic compound with an exocyclic donor atom directly bonded to the heterocyclic ring (e.g., 2-Mercaptobenzothiazole and 3-Methyl-5-pyrazolone), or an cxocyclic donor atom that is not directly bonded to the heterocyclic ring (e.g., 8-Hydroxyquinoline and 8-Hydroxyquinaldine).

In one non-limiting example, the first corrosion inhibitor can be phenyl phosphonic acid, and the second corrosion inhibitor can be 2-Mercaptobenzothiazole. In another non-limiting example, the first corrosion inhibitor can be phenyl phosphonic acid, and the second corrosion inhibitor can be 8-Hydroxyquinoline.

In certain embodiments, the corrosion inhibiting composition 10 of FIG. 4 can include a second carrier 15 b including a first organic corrosion inhibitor 20 b, and a third carrier 15 c including a second organic corrosion inhibitor 20 c that is different from the first organic corrosion inhibitor 20 b. The second carrier 15 b and the third carrier 15 c may be formed as microparticles that are degradable in a corrosive environment. For example, a first carrier body 17 a, a second carrier body 17 b and a third carrier body 17 c of the respective first carrier 15 a, the second carrier 15 b and the third carrier 15 c can be formed of degradable materials. It will be appreciated that the first carrier body 17 a, the second carrier body 17 b, and the third carrier body 17 c can be formed of the same or different materials. In a non-limiting example, the first corrosion inhibitor 20 b and the second corrosion inhibitor 20 c can be chelating agents or capable of acting as chelating agents. In a non-limiting example, the first corrosion inhibitor 20 b can be an organic compound including a ring structure, and the second corrosion inhibitor 20 c can be an organic compound including a ring structure. For example, the first corrosion inhibitor 20 b and the second corrosion inhibitor can 20 c each have a plurality of donor atoms. In a non-limiting example, one or both of the corrosion inhibitors 20 b, 20 c can include(s) a heterocyclic compound with an endocyclic donor atom and an exocyclic donor atom. In a non-limiting example, the first corrosion inhibitor 20 b can include a heterocyclic compound with an exocyclic donor atom directly bonded to the heterocyclic compound (including, but not limited to 2-Mercaptobenzothiazole and 3-Methyl-5-pyrazolone), and the second corrosion inhibitor can include an exocyclic donor atom that is not directly bonded to the heterocyclic compound (including, but not limited to 8-Hydroxyquinoline and 8-Hydroxyquinaldine).

In a non-limiting example, a first organic corrosion inhibitor can be 8-hydroxyquinoline (structure shown below) or a derivative thereof, 8-hydroxyquinaldine or a derivative thereof, or any combination thereof. 8-hydroxyquinoline is a bidentate binding unit containing both an oxygen donor atom (exocyclic donor), and a nitrogen donor atom (endocyclic donor). 8-hydroxyquinoline is capable of acting as a chelating agent and may have the structure shown below when bound to a metal atom, M.

The second organic corrosion inhibitor can be 2-mercaptobenzothiazole or a derivative thereof, 2-mercaptobenzimidazole or a derivative thereof, 2-(benzothiazol-2-ylsulfanyl)-succinic acid or a derivative thereof, or a combination thereof. 2-mercaptobenzothiazole is a bidentate binding unit containing both a sulfur donor atom (exocyclic donor), and a nitrogen donor atom (endocyclic donor).

A variety of methods are known for forming the carrier 15, such as microcapsules and microparticles.

In certain embodiments, hydrophilic-core microcapsules, such as water-core microcapsules, can be formed from emulsions having hydrophilic-phase droplets dispersed in a hydrophobic substance. One example is water-in-oil emulsions. Water-in-oil emulsions include hydrophilic-phase droplets (e.g., as the dispersed phase) dispersed in the hydrophobic phase (e.g., as the continuous phase). If a compound (active substance) is hydrophilic, or it can be dissolved or dispersed in a hydrophilic solvent (e.g. water), then it can be possible to encapsulate it in hydrophilic-core microcapsules. When a compound does not have sufficient solubility in the hydrophilic solvent, a co-solvent can be used to improve the dissolution of the compound and to facilitate the encapsulation process. Similarly, when a compound cannot be dispersed into the hydrophilic phase to form a reasonably stable suspension (e.g., indicated by droplets of the compound being dispersed throughout the hydrophilic phase and the compound remaining dispersed during emulsion formation and encapsulation processes), a surfactant can be used to improve the dispersion of the compound and facilitate the encapsulation process. So if a compound can be dissolved or dispersed in a hydrophilic solvent, with or without the aid of a co-solvent or a surfactant, it is possible to encapsulate it into hydrophilic-core microcapsules.

Hydrophilic-core microcapsules are typically used for encapsulating water-soluble materials, but not oil-soluble materials, such as non-polar molecules. Oil-soluble materials can be incorporated into hydrophilic-core microcapsules by first adding them to a co-solvent, and then adding the resulting solution to the hydrophilic phase. Alternatively, a surfactant can be added to the hydrophilic phase. This will dissolve or disperse the non-polar or oil-soluble reagents into the hydrophilic phase. The emulsion (e.g. water-in-oil emulsion) can then be formed by adding the hydrophilic phase to a hydrophobic phase and a reaction can be initiated to encapsulate the oil, with the active substance dissolved or dispersed therein, into the core of the hydrophilic-core microcapsules.

In general, oil-core as well as water-core microcapsules can formed to include a film-forming compound 21 within the core, being encapsulated by a carrier body 17, such as by a polymeric shell (e.g., see FIG. 2). Alternatively, the film-forming compound 21 in an oil-core microcapsule can be dissolved or dispersed in a hydrophobic substance, such as oil, with or without the aid of a co-solvent or a surfactant. The film-forming compound 21, of a water-core microcapsule, can be dissolved or dispersed in water, with or without the aid of a co-solvent or the aid of a surfactant. Other active ingredients including, but not limited to, a dye, a corrosion indicator, an inorganic corrosion inhibitor, a film-forming compound, or various combinations thereof may be included within the carrier body 17.

The polymeric shell or solid binder of either oil-core or water-core microcapsules or microparticles can include a polymer formed from an encapsulant-forming compound (e.g., precursor) that can include a cross-linking agent having one or more ester and mercapto groups and/or a film-forming pre-polymer. In certain embodiments, an encapsulant-forming compound can include about 5 to about 75 percent (e.g., about 20 to about 50 percent) by weight of a cross-linking agent and about 25 to about 95 percent (e.g., about 50 to about 80 percent) by weight of a film-forming pre-polymer. Examples of the cross-linking agent include, but are not limited to, pentaerythritol tetrakis(2-mercaptoacetate) or compounds with similar structure (e.g., pentaerythritol tetrakis(3-mercaptopropionate) (PTT), pentaerythritol, dipentaerythritol, dipentaerythritol pentaacrylate tetra(mercaptoacetate), pentaerythritol tetra(acrylate), and their derivatives. As described herein, examples of the film-forming pre-polymer can include, but are not limited to, urea formaldehyde pre-polymer resin (e.g., butylated urea-formaldehyde resin, such as CYMEL® U80), melamine formaldehyde resin, polyurethane pre-polymers, polyols, or film-forming monomers, such as urea and formaldehyde solution, melamine and formaldehyde solution, isocyanates and various glycols, etc. The encapsulant-forming compound can form the shells of the oil-core as well as the water-core microcapsules, or the solid binders of microparticles as described herein.

The microcapsule shell of either oil-core or water-core microcapsules can include one or more chemical bonds due to the ester group in the cross-linking agent that are cleavable (e.g., broken down) at ambient temperature when the surrounding pH changes due to the occurrence of a corrosion process. For example, the ester groups can undergo an irreversible hydrolysis reaction under basic pH, e.g., when exposed to an alkali.

Cross-linking agents that have three or four functional groups, such as pentaerythritol tetrakis(2-mercaptoacetate), penta erythritol tetrakis(3-mercaptopropionate) (PTT), pentaerythritol, dipentaerythritol, dipentaerythritol pentaacrylate tetra(mercaptoacetate), and pentaerythritol tetraacrylate can also provide chemical resistance (e.g. solvent resistance) to the microcapsule shells.

It will be appreciated that a number of suitable techniques are available to form the microcapsules and microparticles as described herein, including those methods further described in U.S. Pat. Nos. 7,569,625, 7,790,225 and U.S. Patent Application Publication Nos. 2010/0320421, 2010/0305234, 2012/0207921 and 2013/0017612.

In certain embodiments, corrosion inhibitors once released from respective carriers (e.g., microparticles/microcapsules) can adhere or attach to an exposed surface of a metal substrate (e.g., steel door of an automobile) to provide an anti-corrosion barrier. In certain embodiments, such organic corrosion inhibitors can be absorbed or adsorbed into the surface of the metal substrate providing effective corrosion resistance. In certain embodiments, corrosion inhibiting compositions described herein can also be added to a coating base to form a protective coating which can be applied to these metal substrates.

As shown in FIG. 6, surface 26 of a metal substrate 30 is shown overlaid with multiple layers of coatings 12, 14, 16 and 18 (e.g., paints), collectively indicated as 40, with layer 18, immediately adjacent to the surface 26 of a metal substrate 30, incorporating carriers 15 comprising either film-forming compounds 21 or corrosion inhibitors 20. Metal substrate 30 can, for example, be an outer door panel of a vehicle (e.g., automobile). For coating systems, self-healing or protective coatings can be fabricated by adding carriers containing at least one “self-healing” compound (including, for example, corrosion inhibitors) to commercially available paint primers. Paint primers can include cathodic electrodeposition coatings. Such carriers can release the self-healing compound or compounds when the coating system is damaged. Such damage can occur when the coating is mechanically damaged or suffers corrosive damage.

Coatings, like paint, can include a mixture of solids and a suitable binder, possibly also incorporating a solvent, which can generally be applied to a surface as a thin liquid layer and forms a closely adherent coating on the surface when the liquid layer is “cured”. Paint formulations vary widely. For example, a solvent can be an organic liquid, or water or can be eliminated entirely by applying the paint solids in powder form, relying on electrostatic attraction to build a thin layer. Many automotive paints employ water as a solvent and are referred to as “water-based”. Irrespective of the solvent however, in one example, automotive paints can be cured by exposure to heat in a paint bake oven.

Automotive coatings 40 can include a single layer or comprise multiple layers (e.g., four layers represented as layers 12, 14, 16 and 18 in FIG. 4). In general, layer 18 immediately adjacent to surface 26 of a metal substrate 30 can be generally intended to provide corrosion protection once the automotive coatings 40 have suffered damage. One method of applying layer 18 can be via electrodeposition (or e-coating), but it will be appreciated by one skilled in the art, that a variety of other suitable coating techniques to apply layer 18 can be employed (e.g., spraying, brushing, rolling, etc.). Subsequent layers can include: a primer-surfacer, such as represented by 16, to smooth out surface irregularities, improve stone-chip performance, and help protect against visible and UV light; a basecoat, such as represented by 14, to provide color and aesthetic effects; and a clearcoat, such as represented by 12, to provide primary protection against environmental effects and imparts gloss and depth to the overall paint finish. These three coatings can be applied as liquid sprays. All three coatings can be applied without intermediate high temperature exposure or cure, a procedure commonly described as ‘wet on wet’, and cured in a single paint bake oven. However, layer 18 can be cured separately in a separate paint bake oven prior to applying the remaining layers. Thus, typical automobile painting practice will expose painted parts to the elevated temperatures required for paint baking at least twice. However, it will be appreciated that there are a variety of suitable methods and techniques of applying coatings (e.g., paint layers) to surfaces of a metal body part of a vehicle.

The coating of layer 18 can include a coating base 19 and one or more additives such as a plurality of carriers 15 (e.g., microcapsules and microparticles). The coating base 19 can be a solvent, such as an aliphatic hydrocarbon (e.g., aliphatic petroleum distillates). Other such coating bases 19 (e.g., paint primers) can include greases, lubricants, varnishes, lacquers, shellacs, waxes, polishes, polyurethanes, oil-based enamels, enamel undercoater, latex acrylics, acrylic-based formulations, epoxy-based formulations (e.g., epoxy isocyanate resins), and other suitable combinations thereof Other suitable coating bases are described in U.S. Pat. Nos. 5,070,174, 7,612,152 and 7,723,405. Carriers 15 can be dispersed into a coating base 19 using a variety of suitable techniques (e.g., by mixing, chemical dispersion agents, etc.). Suitable methods of dispersing microcapsules into a coating base are described in U.S. Patent Application Publication No. 2011/0064941. A coating can comprise about 0.1% by weight or more of carriers. In certain embodiments, a coating can comprise about 0.5% by weight or more of carriers; in certain embodiments, about 1.0% by weight or more of carriers; in certain embodiments, about 2.5% by weight or more of carriers; in certain embodiments, about 5.0% by weight or more of carriers; in certain embodiments, about 7.5% by weight or more of carriers; and in certain embodiments, about 10% by weight or more of carriers. It will be understood that a coating can include materials or substances in addition to the coating base and carriers. For example, a coating can include one or more agents that facilitate improvements in the properties of the coating, or a coating can include a filler to increase the volume or mechanical integrity of the coating.

In certain embodiments, a coating base can include a copolymer that includes an epoxy-group, such as an epoxy resin. Epoxy-groups can have a molecular weight of about 100 or more; in certain embodiments, of about 500 or more; in certain embodiments, of about 750 or more; in certain embodiments, of about 1,000 or more; in certain embodiments, of about 1,250 or more; in certain embodiments, of about 1,500 or more; and in certain embodiments of about 2,000 or more. Epoxy-groups can have a molecular weight of about 100,000 or less; in certain embodiments, of about 50,000 or less; in certain embodiments, of about 20,000 or less; in certain embodiments, of about 15,000 or less; in certain embodiments, of about 10,000 or less; in certain embodiments, of about 7,500 or less; in certain embodiments, of about 5,000 or less; and in certain embodiments of about 4,000 or less. It will be appreciated that a number of techniques are known to calculate the molecular weight of suitable epoxy-groups and copolymers.

A coating base can include the dry portion of a coating which does not include the carriers. A coating can comprise about 75% by weight or more of a coating base. In certain embodiments, a coating can comprise about 80% by weight or more of a coating base; in certain embodiments, about 85% by weight or more of a coating base; in certain embodiments, about 90% by weight or more of a coating base; in certain embodiments, about 95% by weight or more of a coating base; in certain embodiments, about 97.5% by weight or more of a coating base; in certain embodiments, about 99% by weight or more of a coating base; in certain embodiments, about 99.5% by weight or more of a coating base; and in certain embodiments, about 99.9% by weight or more of a coating base.

A coating can have a thickness of about 5 gm or more; in certain embodiments, of about 10 gm or more; in certain embodiments, of about 15 gm or more; in certain embodiments, of about 25 gm or more; in certain embodiments, of about 50 gm or more; in certain embodiments, of about 100 gm or more; in certain embodiments, of about 150 gm or more; in certain embodiments of about 200 gm or more; and in certain embodiments of about 300 gm or more. In certain embodiments, a coating can have a thickness of about 10 gm to about 100 pm. In certain embodiments, a coating can have a thickness of about 5 gm to about 25 gm.

To assist in locating corrosive damage to a coating, corrosion indicators can also be included as an encapsulate in a carrier. Suitable corrosion indicators can include a pH indicator that changes color over the alkaline region (e.g., pHs above about 8), such as phenolphthalein. Other suitable corrosion indicators can include ones that fluoresce, such as 7-hydroxycoumarin or coumarin, in the presence of or upon the oxidation of a metal or in the presence or upon the formation of a metal cation complex.

In certain embodiments, where a coating is applied, carriers can include one or more film-forming compounds, corrosion inhibitors, corrosion indicators, or various combinations thereof. For certain embodiments, if a coating is exposed to trauma that carriers to break or rupture, a film-forming compound in the carrier can be released to cover at least a portion of the surface area suffering the trauma and then acts to reduce the degree of any exposed metal of corroding. For certain embodiments, a corrosion inhibitor in a carrier can also be released to act to further reduce the degree of corrosion of any exposed metal.

Note that if corrosion occurs at locations away from the trauma location due to small breaks in the coating, such as chips, or other coating defects, corrosion inhibitors and film-forming compounds can be released due to encapsulants breaking down in the presence of the basic condition, resulting from the corrosion.

In certain embodiments, a portion of carriers in a coating can contain corrosion inhibitors and another portion of carriers in the coating can contain film-forming compounds. In certain embodiments, a portion of carriers in a coating can contain corrosion inhibitors, another portion of carriers in the coating can contain film-forming compounds, and yet another portion of carriers in the coating can contain corrosion indicators. For certain embodiments, carriers having different contents are randomly distributed within a coating base so that carriers having the different functions of indicating, inhibiting, and/or film-forming can be adjacent each other, as well as carriers having like functions being adjacent to each other. For certain embodiments, the different functions of encapsulates can be incorporated into a coating by encapsulating different encapsulates into the same carriers.

In an embodiment, the corrosion inhibiting composition 10 may be applied in an organic matrix between two substrates. In a non-limiting example, the organic matrix may be an adhesive. In a non-limiting example, the substrates may be different metals or metal alloys such as aluminum and steel. In another non-limiting example, one substrate may be a metal or metal alloy and the other substrate may be a polymeric substrate. The polymeric substrate may include fiber reinforcements.

Procedures

A. Hot Salt Water Test

The hot salt water test can measure the amount of corrosion suffered by a metal substrate by measuring the amount of creep that occurs at the tested area.

To measure the amount of creep suffered by a test piece (e.g., metal substrate), an X-cut must first be made to the test piece, such that the X-cut reaches the base material of the test piece. A cutting knife shall be used to make the X-cut. The X-cut shall have a cross angle from 60° to 90°. The cutting knife shall be SK2 and have a hardness of HV 820+/−30. Verify the X-cut by applying electric current. Immerse the test piece in 5 wt % NaCl solution at 55° C. in a glass container, and seal the container tightly. After 240 hours, remove the test piece from the container, then immediately rinse and wipe it lightly with a soft cloth. Check test piece for any rust, blisters or peeling. If rust or blister is found, measure the blister width. Then immediately attach a piece of adhesive tape to the flaw area, and peel it off in the manner specified in Adhesion Test (see below). The adhesive tape shall be cellophane and be 12 or 24 mm in width (e.g., Nichiban Cellotape). If peeling is found, measure the maximum peeling width, and that should be the peeling width. Record either the blister width or the peeling width, whichever is larger, as the blister width/peeling width, otherwise known as the creep value (measured in mm)

In certain embodiments, a coating exhibits a creep value according to the Hot Salt Water Test of about 0.8 mm or less; in certain embodiments, about 0.6 mm or less; in certain embodiments, about 0.4 mm or less; in certain embodiments, about 0.2 mm or less; and in certain embodiments, that is negligible (essentially zero).

B. Adhesion Test

Attach a 12 or 24 mm wide piece of cellophane adhesive tape (e.g., Nichiban Cellotape) to the coating film surface of a test piece carefully not to leave any bubble between them. Hold one edge of the adhesive tape so that the angle between the adhesive face of the tape and the test piece is approximately 45° as shown in FIG. 7, and peel the tape off the test piece rapidly in the same direction.

C. Salt Spray Test

The salt spray test can measure the amount of corrosion suffered by a metal substrate by measuring the amount of creep that occurs at the tested area.

To measure the amount of creep suffered by a test piece (e.g., metal substrate), an X-cut must first be made to the test piece, such that the X-cut reaches the base material of the test piece. A cutting knife shall be used to make the X-cut. The X-cut shall have a cross angle from 60° to 90°. The cutting knife shall be SK2 and have a hardness of HV 820+/−30. Verify the X-cut by applying electric current. Affix the test piece on a salt spray tester at 15° to 30° to the vertical line, and subject it to spraying of 5.0 wt % NaCl solution for 960 hours. The salt spray tester shall conform to ASTM B117 standard. The salt spray tester shall have the test conditions as shown in the table below.

Tester operation method Continuous Test chamber 35 ± 1° C. Air saturator temperature 47 ± 1° C. Relative humidity of test chamber 95 to Spraying pressure 70 to 180 kPa (0.7 to 1.8 kgf/cm²) Amount of solution collected from 0.85 to 2.0 mL/hour for 80 cm² pH of solution made by spraying 6.5 to 7.2

After the subjecting the test piece to the salt spray tester, rinse the test piece and clear the corrosion product using a sponge or scrubbing cloth. Measure the width of the largest swollen area of the X-cut. After leaving the test piece at room temperature for two hours, check the film peeling property by attaching a 12 or 24 mm wide adhesive tape (e.g., Nichiban Cellotape) and peeling it off as specified in Adhesion Test described above. Measure the width of the largest area of the coating film peeled with the tape. Record the width of either the blistered area or peeled area, whichever is larger, as the creep value (measured in mm)

In certain embodiments, a coating exhibits a creep value according to the Salt Spray Test of about 1.6 mm or less; in certain embodiments, about 1.3 mm or less; in certain embodiments, about 1.1 mm or less; in certain embodiments, about 1.0 mm or less; and in certain embodiments, about 0.8 mm or less.

EXAMPLES

For the examples provided below, an epoxy-based coating (e.g., film layer) having a plurality of carriers (some with corrosion inhibitors and some without) was applied (baked at 170° C. for 20 minutes) to a steel sample formed from zinc phosphated steel. The coatings were applied using a draw down bar method to a thickness of 25 microns. The epoxy-based coating included a coating base formed from a BPA epoxy resin, isocyanate and methyl isobutyl ketone (MIBK). The carriers having film-forming compounds were formed as microcapsules. The plurality of microcapsule carrier bodies were formed of polyurethane/urea formaldehyde. The average outer diameter of the film forming microcapsules were 5 μm. The carriers having corrosion inhibitors were formed as microparticles. The plurality of microparticle carrier bodies were formed of melamine formaldehyde/pentaerythritol tetrakis. The average outer diameter of the corrosion inhibiting microparticles were 1 μm. The amount of carrier in each coating was provided as a % wt. of the coating and was measured on a dry basis. A creep value was measured and recorded three times using the Hot Salt Water Test and the Salt Spray Test for the comparative and inventive examples, and the average of those three trials was provided below in Table 1.

TABLE 1 Amount of carrier in Hot Salt Salt Spray coating Water Test Test Creep Corrosion Film-Forming (% wt. on a Creep Value Value Coatings inhibitor(s) Compound dry basis) (mm) (mm) Comparative None None 0 0.8 1.7 Example A Comparative None 50/50 Epoxy 5 1.1 1.2 Example B Resin and Ethyl Phenyl Acetate Blend Comparative None 50/50 Epoxy 2.5 0.5 1.1 Example C Resin and Ethyl Phenyl Acetate Blend Comparative None 50/50 Epoxy 1.0 0.2 1.3 Example D Resin and Ethyl Phenyl Acetate Blend Comparative None 50/50 Alkyd 5 1.5 1.5 Example E Resin and Ethyl Phenyl Acetate Blend Comparative None 50/50 Alkyd 2.5 0.7 1.4 Example F Resin and Ethyl Phenyl Acetate Blend Comparative None 50/50 Alkyd 1.0 0.2 1.1 Example G Resin and Ethyl Phenyl Acetate Blend Inventive 8-Hydroxyquinoline/2- 50/50 Epoxy 4/1/2.5* negligible 1.2 Example H Mercaptobenzothiazole Resin and Ethyl Phenyl Acetate Blend Inventive 8-Hydroxyquinoline/2- 50/50 Alkyd 4/1/2.5* negligible 1.2 Example I Mercaptobenzothiazole Resin and Ethyl Phenyl Acetate Blend *Indicates the individual % wt. for each corrosion inhibitor and film-forming compound, and total % wt. can be calculated by adding the values together.

As illustrated in Table 1, Comparative Examples A-G each exhibited creep values according to the Hot Salt Water Test described herein of 0.2 mm or greater. Inventive Examples H and I each exhibited a negligible (essentially zero) creep value according to the Hot Salt Water Test described herein.

Also shown in Table 1, Inventive Examples H and I also maintained creep values according to the Salt Spray Test described herein at least as low as any of the Comparative Examples A-G.

Inventive Examples H and I provide alternatives to traditional coatings to protect metal substrates, and offer substantial improvements in preventing or inhibiting corrosion.

The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”

It should be understood that every maximum numerical limitation given throughout this specification includes every lower numerical limitation, as if such lower numerical limitations were expressly written herein. Every minimum numerical limitation given throughout this specification will include every higher numerical limitation, as if such higher numerical limitations were expressly written herein. Every numerical range given throughout this specification will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein.

All documents cited in the Detailed Description are, in relevant part, incorporated herein by reference; the citation of any document is not to be construed as an admission that it is prior art with respect to the present invention. To the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention. 

What is claimed is:
 1. A corrosion inhibiting composition comprising: a first plurality of carriers having a first average outer diameter, each comprising a first carrier body and a film forming compound, the first carrier body encapsulating the film forming compound, wherein the first carrier body is formed of a first degradable material; and a second plurality of carriers having a second average outer diameter, each comprising a second carrier body and first corrosion inhibitor, the second carrier body encapsulating the first corrosion inhibitor, wherein the second carrier body is formed of a second degradable material that is different from the first degradable material, and wherein the first average outer diameter is different from the second average outer diameter.
 2. The corrosion inhibiting composition of claim 1, wherein the ratio of the first plurality of carriers to the second plurality of carriers is greater than
 1. 3. The corrosion inhibiting composition of claim 1, wherein the ratio of the first plurality of carriers to the second plurality of carriers is less than
 1. 4. The corrosion inhibiting composition of claim 1, wherein the ratio of the first plurality of carriers to the second plurality of carriers is about
 1. 5. The coating of claim 1, wherein the first average outer diameter is from about 1μm to about 2μm.
 6. The coating of claim 1, wherein the second average outer diameter is from about 0.1μm to about 0.5μm.
 7. The coating of claim 1, wherein the second average outer diameter is from about 3μm to about 5μm.
 8. The corrosion inhibiting composition of claim 1, wherein the second plurality of carriers comprises microparticles wherein the first corrosion inhibitor is released from within the second carrier body upon chemical cleavage of the second degradable material. 